I am not sure what you are asking. 8mm (whether standard or Hi8) require a 8mm (or Hi8) deck to play. There is not adapter that will let them play in a VHS VCR.

Perhaps you are thinking of VHS-C, which is a miniature cassette that still uses the same tape as standard VHS tapes. These can be put in an adapter and then played directly in a standard VHS videotape deck.

If you want to transfer the video from 8mm or Hi8 tapes to VHS, you can do this by connecting the composite or S-Video output from the 8mm deck to a VHS deck and then pressing PLAY on the 8mm deck and RECORD on the VHS deck. For best results, you should use a timebase corrector between the two decks.

You can also capture the 8mm tape to the computer, by connecting the composite or S-Video cable from the 8mm deck to your DV or Digital8 camcorder, and then connecting the Firewire output of the camcorder to your computer. You then can edit the video and put it back out to VHS videotape. I think you get far better results than just simply doing a tape copy because the digitizing process performs some of the same magic as does the timebase corrector: The signal going back from the computer to the deck is completely regenerated and the timebase signals the recording deck sees have nothing to do with the signals that went into the computer in the first place. It's not quite the same as a timebase corrector, but the tapes you make in this way will suffer far less "generation loss" than if you just copied from one deck directly to the other without a timebase corrector.